package com.bib.essensbestellungsverwaltung;

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.ArrayList;
import java.util.Base64;
import java.util.List;

/**
 * A collection of functions loosely related to account management
 * Acts as an abstraction layer to the database
 * @author Malte Schulze Hobeling
 */
public class AccountMgr {

    /**
     * creates a user with createUser(...) and adds its id to the 'worker' table
     * @param worker the worker to be created
     * @return userid or -1
     * @author Malte Schulze Hobeling
     */
    protected static long createWorker(Worker worker){
        long id = createUser(worker);
        String sId = String.valueOf(id);
        Database.insert("worker", new String[]{"userid"}, new String[]{sId});
        return id;
    }

    /**
     * creates a user with createUser(...) and adds its id to the 'parent' table
     * @param parent the parent to be created
     * @return userid or -1
     * @author Malte Schulze Hobeling
     */
    protected static long createParent(Parent parent){
        long id = createUser(parent);
        String sId = String.valueOf(id);
        Database.insert("parent", new String[]{"userid"}, new String[]{sId});
        return id;
    }

    /**
     * adds a user to the database
     * @param user the user to be created
     * @return userid or -1
     * @author Malte Schulze Hobeling
     */
    protected static long createUser(User user) {
        String[] userH = {"name", "firstname", "addressid", "password", "email"};
        String name = user.getName();
        String firstname = user.getFirstname();
        String pw = hashAndSalt(user.getPassword(), getSalt());
        String email = user.getEmail();
        long addressId = user.getAddress().getId();
        if(addressId < 1){
            addressId = createAddress(user.getAddress());
        }
        String[] userD = {name, firstname, String.valueOf(addressId), pw, email};
        return Database.insert("user", userH, userD);
    }

    /**
     * adds an address to the database
     * @param address the address to be created
     * @return id or -1
     * @author Malte Schulze Hobeling
     */
    protected static long createAddress(Address address){
        String[] addressH = {"street", "number", "plz", "city"};
        String[] addressD = {address.getStreet(),address.getNumber(),address.getPlz(),address.getCity()};
        return Database.insert("address",addressH,addressD);
    }

    /**
     * adds a child and allergies to the database
     * @param child the child to be created
     * @return id of child or -1
     * @author Malte Schulze Hobeling
     */
    protected static long createChild(Child child){
        String[] childH = {"name","firstname","addressid"};
        String[] childD = {child.getName(), child.getFirstname(), String.valueOf(child.getAddress().getId())};
        long id = Database.insert("child", childH, childD);
        String[] child_allergyH = {"childid","allergyid","severityid"};
        for (AllergySeverity allergy: child.getAllergies()) {
            String sId = String.valueOf(id);
            String sAllergyId = String.valueOf(allergy.getAllergy().getId());
            String sSeverityId = String.valueOf(allergy.getSeverityId());
            String[] child_allergyD = {sId,sAllergyId,sSeverityId};
            Database.insert("child_allergy",child_allergyH,child_allergyD);
        }
        return id;
    }

    /**
     * returns a User(Worker | Parent) for a given id or null if no unique id was found
     * @param id id of the User
     * @return User(Worker | Parent) or null
     * @author Malte Schulze Hobeling
     */
    protected static User getUserById(long id){
        List<String> entry = Database.getEntryById("user",id);
        if(entry.size() != 1){
            return null;
        }
        String[] parts = entry.get(0).split(":");
        Address address = getAddressById(id);
        if(isWorker(String.valueOf(id))){
            return new Worker(id,parts[1],parts[2],parts[4],parts[5],address);
        }else{
            String[] parent_childH = {"parentuserid"};
            String[] parent_childD = {String.valueOf(id)};
            List<Child> children = new ArrayList<>();
            List<String> parent_childEntries = Database.select("parent_child",parent_childH,parent_childD);
            for (String parent_childEntry: parent_childEntries) {
                String[] parent_childParts = parent_childEntry.split(":");
                children.add(getChildById(Long.parseLong(parent_childParts[2])));
            }
            return new Parent(id,parts[1],parts[2],parts[4],parts[5],address,children);
        }
    }

    /**
     * returns a Child for a given id or null if no unique id was found
     * @param id id of child
     * @return Child or null
     * @author Malte Schulze Hobeling
     */
    protected static Child getChildById(long id){
        List<String> entry = Database.getEntryById("child",id);
        if(entry.size() != 1){
            return null;
        }
        String[] parts = entry.get(0).split(":");
        String[] child_allergyH = {"childid"};
        String[] child_allergyD = {String.valueOf(id)};
        List<String> entriesAllergy = Database.select("child_allergy",child_allergyH,child_allergyD);
        List<AllergySeverity> allergySeverities = new ArrayList<>();
        for (String entryAllergy : entriesAllergy) {
            String[] allergyParts = entryAllergy.split(":");
            List<String> severity = Database.getEntryById("severity", Long.parseLong(allergyParts[3]));
            String sSeverity = severity.get(0).split(":")[1];
            long lSeverity = Long.parseLong(severity.get(0).split(":")[0]);
            allergySeverities.add(new AllergySeverity(FoodMgr.getAllergyById(Long.parseLong(allergyParts[2])),lSeverity,sSeverity));
        }
        return new Child(id,parts[1],parts[2],getAddressById(Long.parseLong(parts[3])),allergySeverities);
    }

    /**
     * returns an Address for a given id or null if no unique id was found
     * @param id id of the address
     * @return Address or null
     * @author Malte Schulze Hobeling
     */
    protected static Address getAddressById(long id){
        List<String> entry = Database.getEntryById("address",id);
        if(entry.size() != 1){
            return null;
        }
        String[] parts = entry.get(0).split(":");
        return new Address(Long.parseLong(parts[0]),parts[1],parts[2],parts[3],parts[4]);
    }

    /**
     * creates entries in the database to match parent to child
     * @param parentId id of parent
     * @param childId id of child
     * @return id of parent_child or -1
     * @author Malte Schulze Hobeling
     */
    protected static long matchParentChild(String parentId, String childId){
        String[] parent_childH = {"parentuserid","childid"};
        String[] parent_childD = {parentId,childId};
        return Database.insert("parent_child", parent_childH,parent_childD);
    }

    /**
     * a simple login to check if a given email matches a password
     * @param email email
     * @param pw password
     * @return id or -1
     * @author Malte Schulze Hobeling
     */
    protected static long login(String email, String pw){
        String[] pwH = {"email"};
        String[] pwD = {email};
        List<String> foundEmail = Database.select("user",pwH,pwD);
        String salt;
        if(foundEmail.size() == 1){
            String[] userParts = foundEmail.get(0).split(":");
            String[] pwParts = userParts[4].split("\\.");
            salt = pwParts[1];
        }else{
            //no unique user found; still calculating a hash for security reasons
            salt = getSalt();
        }
        String[] userH = {"email","password"};
        String[] userD = {email,hashAndSalt(pw,salt)};
        return Database.getSingleId("user",userH,userD);
    }

    /**
     * checks if id is in worker table
     * @param id userid
     * @return true if id is in worker table
     * @author Malte Schulze Hobeling
     */
    protected static boolean isWorker(String id){
        String[] workerH = {"userid"};
        String[] workerD = {id};
        long workerId = Database.getSingleId("worker",workerH,workerD);
        return workerId > 0;
    }

    /**
     * checks if id is in parent table
     * @param id userid
     * @return true if id is in parent table
     * @author Malte Schulze Hobeling
     */
    protected static boolean isParent(String id){
        String[] parentH = {"userid"};
        String[] parentD = {id};
        long parentId = Database.getSingleId("parent",parentH,parentD);
        return parentId > 0;
    }

    /**
     * returns a hashed and salted password
     * @param pw the password to hash
     * @return hashed and salted password
     * @author Malte Schulze Hobeling
     */
    private static String hashAndSalt(String pw, String salt){
        Base64.Decoder dec = Base64.getDecoder();
        byte[] bySalt = dec.decode(salt);
        KeySpec spec = new PBEKeySpec(pw.toCharArray(), bySalt,310001,256);
        String hashedPw;
        try {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
            byte[] hash = factory.generateSecret(spec).getEncoded();
            Base64.Encoder enc = Base64.getEncoder();
            hashedPw = enc.encodeToString(hash);
        } catch (InvalidKeySpecException | NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
        hashedPw += "." + salt;
        return hashedPw;
    }

    /**
     * generates a secure random salt, Base64 encoded
     * @return String Base64 encoded
     * @author Malte Schulze Hobeling
     */
    private static String getSalt(){
        SecureRandom sec = new SecureRandom();
        byte[] salt = new byte[16];
        sec.nextBytes(salt);
        Base64.Encoder enc = Base64.getEncoder();
        return enc.encodeToString(salt);
    }

    /**
     * gives the invoice for one month and one child
     * @param date YYYY-MM the month
     * @param childId id of child
     * @return the invoice as a List
     * @author Malte Schulze Hobeling
     */
    protected static List<String> getInvoice(String date, String childId){
        List<String> invoice = new ArrayList<>();
        List<String> child = Database.getEntryById("child", Long.parseLong(childId));
        if(child.size() != 1){
            return invoice;
        }
        invoice.add("Monatsabrechnung " + date);
        String[] childParts = child.get(0).split(":");
        invoice.add(childParts[1] + ", " + childParts[2]);
        String[] food_planH = {"date"};
        String[] food_planD = {date+"%"};
        List<String> food_plan = Database.select("food_plan",food_planH,food_planD);
        for (String day : food_plan) {
            String[] food_planParts = day.split(":");
            String[] food_selectionH = {"childid","food_planid"};
            String[] food_selectionD = {childId,food_planParts[0]};
            List<String> food_selection = Database.select("food_selection",food_selectionH,food_selectionD);
            for (String food_select : food_selection) {
                String[] food_selectParts = food_select.split(":");
                List<String> food = Database.getEntryById("food",Long.parseLong(food_selectParts[3]));
                String[] foodParts = food.get(0).split(":");
                String line = food_planParts[1] + ": " + foodParts[1];
                invoice.add(line);
            }
        }
        double price = getPrice();
        invoice.add("Total: " + (invoice.size()-2) + " X " + price + "€ = " + ((invoice.size()-2)*price) + "€");
        return invoice;
    }

    /**
     * gets the price per meal from the database and converts it to double
     * @return double price
     * @author Malte Schulze Hobeling
     */
    protected static double getPrice(){
        List<String> priceEntry = Database.getEntryById("price",1);
        return Double.parseDouble(priceEntry.get(0).split(":")[1])/100.0;
    }

    /**
     * converts the price per meal to integer and updates it in the database
     * @param price double
     * @author Malte Schulze Hobeling
     */
    protected static void setPrice(double price){
        String[] priceH = {"id","price"};
        String[] priceD = {"1", String.valueOf((int)(price*100))};
        Database.update("price",priceH,priceD);
    }
}